1. Field of the Invention
This invention relates to an automatic cancelling device for blinkers and, in particular, to an automatic cancelling device for electric-type blinkers which is adapted to disengage from a locked position by the attraction of a solenoid even when the blinker operation knob is at a position away from the steering shaft.
2. Description of the Related Art
Generally, an automatic cancelling device for electric type blinkers of the above-mentioned type has a blinker operation lever which is rotated by a blinker operation knob and which is swingably arranged in a case. A driving rod is swingably held by this lever through the intermediation of a compression spring. This driving rod is pressed against an opposite cam, or the cam is pressed against this driving rod by the spring. This cam is equipped with two locking grooves serving to retain the above-mentioned lever at either of two positions respectively corresponding to the right/left blinker switching contacts for causing either the right or the left blinker to flash and a groove situated between these two grooves and serving to retain the lever at its neutral position. The lever can be returned to its neutral position from its left or right position where it has been retained, i.e., from either of its lock positions, by means of a solenoid. This solenoid is adapted to be energized by an unlocking signal and causes the cam to retreat, thereby cancelling the locking and allowing the lever to return to its neutral position. Further, when swinging the lever to its left or right position, the driving rod moves over a step section immediately before it fits into the locking groove, with the result that the operator experiences a clicking feeling when effecting the locking.
In the prior-art structure described above, the driving rod and the cam are pressed against each other, for example, by the resilient force of a compression spring so that the blinker operation lever may be retained or locked in its right, left or neutral position without involving any play. Further, the blinker operation lever is biased toward its neutral position by a return spring so that it may automatically return to its neutral position. Because of the force of this return spring acting on the blinker operation lever, the force of the above-mentioned compression spring is set larger than the force of the return spring so that the locked condition may be maintained. Accordingly, when cancelling the locked condition, the cam has to be moved against the resilient force of the compression spring. This movement requires a large-sized solenoid, making it difficult to reduce the device size and resulting in high production costs.
Further, in this cam, the raised portions of the cam surface in which are formed grooves which are used for locking and unlocking the blinker operation lever (the grooves for locking the lever in its right or left position) and the raised portions of the cam used for resisting the rotation of the blinker operation lever (the raised surfaces positioned immediately before the grooves for locking) are integrally formed, so that the configuration of these highs has an influence on the unlocking operation. Thus, the displacement of the cam effected by the solenoid must be large, which means the solenoid used must be a large-sized one. In addition, the configuration of the cam highs for detention is limited to certain types, so that the operator cannot experience a varied feeling in operation.